Biochemical and hematological changes in low-level aluminum intoxication

Preclinical Pharmacokinetics, Pharmacodynamics and Safety of Sucroferric Oxyhydroxide

Sucroferric oxyhydroxide (VELPHORO^®) is a polynuclear iron-based phosphate binder recently approved for the treatment of hyperphosphataemia in patients with chronic kidney disease (CKD). As a number of the available phosphate binders do not provide the optimal combination of good efficacy, adequate tolerability and low pill burden, sucroferric oxyhydroxide constitutes a promising alternative. Among the attributes of an ideal phosphate binder is minimal absorption and, hence, low risk of systemic toxicity. Accordingly, the iron-releasing properties and absorption, distribution, metabolism and excretion (ADME) profile of sucroferric oxyhydroxide, as well as the possibility of iron accumulation and toxicity, were investigated in a series of preclinical studies. The effect of sucroferric oxyhydroxide on the progression of vascular calcification was also investigated. Sucroferric oxyhydroxide exhibited a high phosphate-binding capacity and low iron-releasing properties across the physiological pH range found in the gastrointestinal tract. In the ADME studies, uptake of ⁵⁹Fe-radiolabelled sucroferric oxyhydroxide was low in rats and dogs (<1% from a 50 mg Fe/kg bodyweight dose), with the majority of absorbed iron located in red blood cells. Long-term (up to 2 years) administration of sucroferric oxyhydroxide in rats and dogs was associated with modest increases in tissue iron levels and no iron toxicity. Moreoever, in uraemic rats, sucroferric oxyhydroxide was associated with reduced progression of vascular calcification compared with calcium carbonate. In conclusion, sucroferric oxyhydroxide offers a new option for the treatment of hyperphosphataemia, with a high phosphate-binding capacity, minimal iron release, and low potential for iron accumulation and toxicity.

Risk factors and consequences of hyperaluminemia in a peritoneal dialysis cohort

BACKGROUND

Widespread Al toxicity is unusual today. In 2005, Canadian peritoneal dialysis (PD) centers reported widespread hyperaluminemia in patients using dialysates from one specific manufacturer. Our objectives were to evaluate risk factors related to Al accumulation and to assess its clinical consequences in patients from 2 centers.

METHODS

A retrospective closed cohort study was conducted in patients treated with PD in May 2005. A multivariate linear regression model was constructed to identify variables associated with a higher serum Al level in the exposed group at the moment of solution change. Using appropriate statistical methods, anemia and bone metabolism parameters were compared between the exposed and unexposed groups. Time to first peritonitis was estimated by the Kaplan-Meier method.

RESULTS

The study cohort included 87 Al-exposed patients and 95 unexposed patients. In the exposed group, serum Al at the moment of solution change was influenced by the length of exposure to Al-containing dialysates and by PD creatinine clearance; serum Al was inversely correlated with renal creatinine clearance. No consequences of Al accumulation were observed. No difference was observed in the time to first peritonitis between patients who switched manufacturers and those who remained with the original manufacturer.

CONCLUSIONS

Our results suggest that hyperaluminemia is directly related to the length and extent of exposure to Al-containing dialysates; residual renal function is protective against Al accumulation. Because the problem was detected rapidly, no clinical consequences of hyperaluminemia were observed in the study cohort.

Phosphate binding therapy in dialysis patients: focus on lanthanum carbonate

Hyperphosphatemia is an inevitable consequence of end stage chronic kidney disease and is present in the majority of dialysis patients. Recent observational data has associated hyperphosphatemia with increased cardiovascular mortality among dialysis patients. Dietary restriction of phosphate and current dialysis prescription practices are not enough to maintain serum phosphate levels within the recommended range so that the majority of dialysis patients require oral phosphate binders. Unfortunately, conventional phosphate binders are not reliably effective and are associated with a range of limitations and side effects. Aluminium-containing agents are highly efficient but no longer widely used because of well established and proven toxicity. Calcium based salts are inexpensive, effective and most widely used but there is now concern about their association with hypercalcemia and vascular calcification. Sevelamer hydrochloride is associated with fewer adverse effects, but a large pill burden and high cost are limiting factors to its wider use. In addition, the efficacy of sevelamer as a monotherapy in lowering phosphate to target levels in severe hyperphosphatemia remains debatable. Lanthanum carbonate is a promising new non-aluminium, calcium-free phosphate binder. Preclinical and clinical studies have demonstrated a good safety profile, and it appears well tolerated and effective in reducing phosphate levels in dialysis patients. Its identified adverse events are apparently mild to moderate in severity and mostly GI related. It appears to be effective as a monotherapy, with a reduced pill burden, but like sevelamer, it is significantly more expensive than calcium-based binders. Data on its safety profile over 6 years of treatment are now available.

Lanthanum carbonate

OBJECTIVE

To review the pharmacology, pharmacokinetics, clinical efficacy, and safety profile of lanthanum carbonate, a phosphate binder for chronic kidney disease (CKD).

DATA SOURCES

Information was selected from PubMed (1965-October 2005). All studies presented as scientific posters and abstracts from nephrology meetings from 1999 to 2005 were also included.

STUDY SELECTION AND DATA EXTRACTION

All published articles regarding lanthanum carbonate were included. In addition, abstracts and presentations from scientific meeting symposia were also considered for inclusion.

DATA SYNTHESIS

Lanthanum carbonate has been recently approved as non-calcium-based therapy for phosphate reduction in patients with stage 5 CKD requiring dialysis. The recommended dose is 250-500 mg with meals, for a maximum of 1500 mg daily. Clinical studies have shown short- and long-term safety with lanthanum carbonate administration. Adverse effects were primarily gastrointestinal in nature. Clinical trials have also shown reductions in serum phosphorus to target concentrations, reductions in associated calcium-phosphorus product, and minimal effects on serum calcium and parathyroid hormone concentrations.

CONCLUSIONS

Lanthanum carbonate is an effective phosphate-binding agent without significant risk of hypercalcemia or worsening metabolic acidosis. Lanthanum carbonate is a safe and effective drug for reduction of elevated serum phosphorus levels associated with stage 5 CKD. The role of lanthanum carbonate relative to other phosphate-binding drugs, such as calcium salts and sevelamer, remains to be determined.

Efficacy, Tolerability, and Safety of Lanthanum Carbonate in Hyperphosphatemia: A 6-Month, Randomized, Comparative Trial versus Calcium Carbonate

BACKGROUND/AIMS

Hyperphosphatemia is an important clinical consequence of renal failure, and its multiple adverse systemic effects are associated with significantly increased risks of morbidity and mortality in dialysis patients. Existing oral phosphate binders have not permitted control of serum phosphate within currently accepted guidelines. This study compares lanthanum carbonate with calcium carbonate for control of serum phosphate in hemodialysis patients.

METHODS

In this European multicentre study, 800 patients were randomised to receive either lanthanum or calcium carbonate and the dose titrated over 5 weeks to achieve control of serum phosphate. Serum levels of phosphate, calcium and parathryoid hormone were followed over the following 20 weeks.

RESULTS

Around 65% of patients in each group achieved phosphate control, but in the calcium carbonate group this was at the expense of significant hypercalcemia (20.2% of patients vs. 0.4%). Consequently, calcium x phosphate product tended to be better controlled in the lanthanum group.

CONCLUSION

This 6-month study demonstrates that serum phosphate control with lanthanum carbonate (750-3,000 mg/day) is similar to that seen with calcium carbonate (1,500-9,000 mg/day), but with a significantly reduced incidence of hypercalcemia. Lanthanum carbonate is well tolerated and may be more effective in reducing calcium x phosphate product than calcium carbonate.

Effects of aluminum sulfate on erythropoiesis in rats

The aim of this study was to investigate the effects of chronically administered aluminum on erythropoiesis in rats. After treatment (i.p. injections of Al(2)(SO(4))(3), 50 micromol/kg body weight, five times a week) for 3 months, the treated (Al) group showed significantly decreased hemoglobin concentration (32%) and hematocrit (24%) compared with the control group. Serum iron decreased significantly in the Al group, whereas total iron binding capacity did not change. Treatment did not alter the activity of hepatic, renal or cerebral delta-ALA-D. Biochemical measurements related to 2-thiobarbituric acid-reactive substance (TBARS) levels from serum and hepatic, renal and cerebral homogenates also did not change after treatment. Hepatic concentrations of aluminum were higher in the Al group than in the control group. Renal and cerebral aluminum concentrations did not vary between groups. The present results indicate that exposure to aluminum sulfate promotes signs of anemia in rats as a consequence of alterations in iron status.